Aircraft engines are known to employ so-called integrated engine oil tanks, i.e. comprising a funnel-shaped body inserted in fluidtight manner inside the tank through an inlet of the tank, and defining an oil feed conduit into the tank; a removable cover body for fluidtight closing one end of the funnel-shaped body; a dipstick housed inside the feed conduit; and a safety valve which prevents oil outflow from the tank along the feed conduit in the absence of the cover body closing the funnel-shaped body.
In known solutions, the safety valve is defined by a spherical body housed inside a bottom end portion of the feed conduit, and movable between a lowered position, allowing oil flow into the tank through the funnel-shaped body, and a raised position, preventing oil outflow along the feed conduit.
Though widely used, known caps of the above type are not altogether satisfactory in terms of performance. In particular, they make filling the tank difficult and slow, do not always allow the desired oil level to be reached inside the tank, and often make it difficult to determine the exact oil level.
This is mainly due to the design of the safety valve, and its location inside the funnel-shaped body. That is, being located at the bottom of the funnel-shaped body, i.e. far below the maximum oil level in the tank, the same safety valve allowing inflow of the oil also prevents air escaping from the tank, and therefore inflow of the oil into the tank, to the extent that the tank may seem full when it actually is not, thus endangering the engine.